1. Field of Invention
This invention relates to visibility, specifically improving observation of darker objects when mixed with or surrounded by brighter or blinding objects.
2. Description of Prior Art
The use of direct vision devices like eyeglasses, sunglasses, mirrors, binoculars, telescopes, goggles and any type of direct view optics, is well known in the art and is used in variety of applications.
The prior art vision enhancing methods for direct view optics operates equally on the entire image (limited by the system Field Of View—FOV).
As an example we can look at the use of prior art car rearview or sideview mirror. The prior art mirror systems, active or passive, reflect the image directly or through an attenuation media. Very bright images, like those seen at night on a car's rearview mirror, can cause the driver to be temporarily blinded, and miss a significant part of the image. By tilting the mirror few degrees, as depicted in FIG. 1a, part of the light is reflected from the mirror surface rather than from the reflective surface behind the glass, thus creating a dimmed image of the entire view. Another type of car mirror has a controlled shutter/filter that changes the entire FOV transparency by electronically driving an Electro-Chromic coating (or other type of controlled transparent material). This prior art lacks the ability to dim just portions of the image (e.g. the blinding spots) and leave the rest of it unchanged.
As another example we can look at the use of prior art sunglasses or eyeglasses. In case where bright objects are surrounded by dark areas (e.g. at night) or where dimmed areas are surrounded by bright environment (during the day) the viewer suffers from blind areas and reduced visibility, due to eyesight adjusting to the average brightness (Eye Iris). The prior art controls the transparency of the glasses by a shutter/filter via an electronic ambient light sensor, which drives an Electro-Chromic coating or by using Opto-Chromic material embedded in the glass activated by the UV when in sunlight environment. Using these methods to adjust the transparency of the glasses allows the entire image to be controlled. This prior art suffers from lack of ability to dim just the blinding spots and leave the rest of image areas in the proper contrast level.
Another yet example is the Auto-dimming mirror prior art, which is using a transparency controlled medium in front of the mirror. The transparency is controlled by utilizing the electro-optic or Electro-Chromic characteristics of the material (FIG. 2). The ambient light sensor [2] located near the system, senses the light, and changes the control voltage at the battery/power source [13]. This voltage change drives the active shutter [12] to the proper transparency, such that the image reflected from the mirror [11] looks dimmed to the viewer's eye [33]. The bright spots [14] and dark areas of interest [15] are dimmed at the same magnitude which prevents blinding the viewer on one hand, but provides a darker and obscured image on the other. This prior art lacks the ability to dim just portions of the image (e.g. the blinding spots, very bright areas, etc.) and leave the darker areas in the proper contrast level.
Another prior art (U.S. Pat. No. 5,760,962 Automatic rearview mirror system using a photosensor array, Schofield, et al., Jun. 2, 1998) controls the reflectivity of the rear and a side view mirrors using a sensor array. This sensor array covers wide FOV for both mirrors. This prior art suffers from a number of disadvantages:
I) when there is blinding light from behind, the sensor array identifies the portion of the image which has a high intensity, and changes the reflectivity of the pertaining mirror segments. However, since the blinding light falls on the entire mirror, the driver will still be blinded if she moves her head, looking at the mirror from a different angle.
II) The sensor or sensors array it utilizes to measure the light intensity is separate from the mirror or attached to a small portion of it, thus requiring alignment with the mirror for proper operation. The herein proposed VEM has a light sensor attached to each light control panel element (pixel), such that only the required pixels are dimmed, without affecting the rest of the picture. Now, even if the driver moves his head he is not blinded, since the path of the light is dimmed before it actually reaches the mirror.
Another prior art Electrically Controllable Optical Filter Element (U.S. Pat. No. 5,510,609, Ackermann, Apr. 23, 1996) contains optoelectric transducer elements, electronic circuit means and a lens that is located in front of the light sensitive sensor only. The only position by which the sensor correlates with the filter elements is when the viewer is looking perpendicular to the plane of the wafer. However, in the case of a car rearview mirror, when a slanted mirror is mounted behind the filter elements, the bright light spots will not be correlated with the reflected image due to driver looking at the mirror from an angle.
Another prior art (U.S. Pat. No. 5,351,151 Optical filter using microlens arrays, Levy, et al, Sep. 27, 1994) controls the light by using arrays of small lenses and nonlinear optical materials to solve the generalized spatial and spectral optical filtering problem. This solution is segmented by using micro lenses array in such that each particular lens on one side of the array needs to align perfectly to the second array.
This prior art suffers from major disadvantage, like distorted and blurred image due to light leaks between the lenses and lack of reconstructing the segmented images into one image. In addition, the transflector materials used with homogeneous layer cause a substantial latency and delay in the response of the filter to changes in light.